This invention relates generally to keyswitches and keyboards and the like and structural arrangements for providing electrical signals in response to actuation of individual ones of the keyswitches.
While various conventional arrangements of keyswitches for keyboards are known, including mechanical, inductive and capacitive, the advantages of prior contactless keyswitches using magnetic coupling, for example, are outweighed by the disadvantage of requiring relatively expensive and complex structure and circuit arrangements for producing output signals representative of actuated keys. In several of the prior art keyboard arrangements, inductive sensing elements of the switches in the keyboard matrix were not able to prevent an electromagnetic force in the secondary coil of a transformer sensing element of the keyswitch. Accordingly, a "dummy" keyboard array was provided to cancel the noise signals in the secondaries. Also, these transformer structural arrangements have a common problem in that the secondary is located in the shadow of the primary and in another plane, e.g. not coplanar which accounts in part for failure to eliminate electromotive forces requiring the duplicate keyboard array or other noise canceling coils.
Further, sensing by one turn elements in separate planes reduces the coupling efficiency substantially so that relatively large driving currents are required. Also, the effectiveness of eddy current shorting by conductive metal is reduced, along with a decrease in signal-to-noise ratio.
The prior art also discloses keyswitch forces applied in line with the keyswitch assembly to displace conductive members and does not show structural arrangements for providing a mechanical advantage to produce a desired large displacement of the conductive shorting member by smaller key stroke travel as provided by the present invention.